Lists in Python

✅ What is a List?

A list is a collection of items in Python. You can think of it like a basket that holds multiple values—like numbers, words, or both.

A list:

• Is ordered (items have a specific position)
• Is changeable (you can add, remove, or update items)
• Allows duplicate values

🟢 How to Create a List

Use square brackets [ ] to create a list:

students = ["ansh", "aarav", "mishti"]
numbers = [1, 2, 3, 4]
mixed = [1, "hello", 3.5, True]

You can also create an empty list:

empty_list = []

🔢 Accessing Items in a List

You can use indexing to access items in a list. Python indexes start from 0.

students = ["ansh", "aarav", "mishti"]
print(students[0])  # ansh
print(students[1])  # aarav

You can also use negative indexing:

print(students[-1])  # mishti (last item)

✏️ Changing List Items

Lists are mutable, meaning you can change values.

fruits = ["apple", "banana", "cherry"]
fruits[1] = "mango"
print(fruits)  # ['apple', 'mango', 'cherry']

➕ Adding Items to a List

append() – adds at the end:

fruits.append("orange")

insert() – adds at a specific position:

fruits.insert(1, "grape")  # inserts at index 1

❌ Removing Items from a List

remove() – removes by value:

fruits.remove("banana")

pop() – removes by index (default is last item):

fruits.pop()     # removes last
fruits.pop(0)    # removes first

clear() – removes all items:

fruits.clear()

🔁 Looping Through a List

You can use a for loop:

for fruit in fruits:
    print(fruit)

📏 Getting Length of a List

Use the len() function:

fruits = ["apple", "banana", "cherry"]
print(len(fruits))  # 3

🔄 Joining Two Lists

Use the + operator to combine two lists:

list1 = [1, 2]
list2 = [3, 4]
combined = list1 + list2  # [1, 2, 3, 4]

🔍 Checking for an Item

Use the in keyword:

if "apple" in fruits:
    print("Yes, apple is in the list")

🧩 List with Different Data Types

A list can have different types of data:

my_list = [10, "hello", True, 3.5]

🧱 Nested Lists

A list can contain another list (called a nested list):

nested = [1, 2, [3, 4]]
print(nested[2])      # [3, 4]
print(nested[2][1])   # 4

🧪 List Methods (Commonly Used)

Method	Description
append()	Adds item at the end
insert()	Adds item at specific index
remove()	Removes item by value
pop()	Removes item by index
clear()	Removes all items
sort()	Sorts the list (ascending by default)
reverse()	Reverses the list
index()	Returns index of first match
count()	Returns number of times item appears

🔃 Sorting a List

numbers = [3, 1, 4, 2]
numbers.sort()        # [1, 2, 3, 4]
numbers.sort(reverse=True)  # [4, 3, 2, 1]

🔁 Copying a List

list1 = [1, 2, 3]
list2 = list1.copy()

🧰 Converting List to Other Types

List to Tuple:

my_list = [1, 2, 3]
my_tuple = tuple(my_list)

✅ Summary

• Lists are used to store multiple items in a single variable
• Lists are ordered and changeable
• You can add, remove, and update items
• Lists support looping, sorting, nesting, and more
• Lists are one of the most commonly used data structures in Python